/***
 * ASM Guide
 * Copyright (c) 2007 Eric Bruneton, 2011 Google
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

package cn.zwy.day4;

import static org.objectweb.asm.Opcodes.ACC_INTERFACE;
import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
import static org.objectweb.asm.Opcodes.ACC_STATIC;
import static org.objectweb.asm.Opcodes.ASM4;

import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.commons.AdviceAdapter;

/**
 * ASM Guide example class.
 * 
 * @author Eric Bruneton
 */
// AdviceAdapter
// 用于在一个方法的开头以及恰在任意 RETURN 或 ATHROW
// 指令之前插入代码。它的主要好处就是对于构造器也是有效的，在构造器中，不能将代码恰好插
// 入到构造器的开头，而是插在对超构造器的调用之后。事实上，这个适配器的大多数代码都专门
// 用于检测对这个超构造器的调用
public class AddTimerAdapter6 extends ClassVisitor {

    private String owner;

    private boolean isInterface;

    public AddTimerAdapter6(ClassVisitor cv) {
        super(ASM4, cv);
    }

    public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
        cv.visit(version, access, name, signature, superName, interfaces);
        owner = name;
        isInterface = (access & ACC_INTERFACE) != 0;
    }

    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
        MethodVisitor mv = cv.visitMethod(access, name, desc, signature, exceptions);
        if (!isInterface && mv != null && !name.equals("<init>")) {
            mv = new AddTimerMethodAdapter6(access, name, desc, mv);
        }
        return mv;
    }

    public void visitEnd() {
        if (!isInterface) {
            FieldVisitor fv = cv.visitField(ACC_PUBLIC + ACC_STATIC, "timer", "J", null, null);
            if (fv != null) {
                fv.visitEnd();
            }
            cv.visitEnd();
        }
    }

    class AddTimerMethodAdapter6 extends AdviceAdapter {

        public AddTimerMethodAdapter6(int access, String name, String desc, MethodVisitor mv) {
            super(ASM4, mv, access, name, desc);
        }

        protected void onMethodEnter() {
            mv.visitFieldInsn(GETSTATIC, owner, "timer", "J");
            mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
            mv.visitInsn(LSUB);
            mv.visitFieldInsn(PUTSTATIC, owner, "timer", "J");
        }

        protected void onMethodExit(int opcode) {
            mv.visitFieldInsn(GETSTATIC, owner, "timer", "J");
            mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
            mv.visitInsn(LADD);
            mv.visitFieldInsn(PUTSTATIC, owner, "timer", "J");
        }

        public void visitMaxs(int maxStack, int maxLocals) {
            super.visitMaxs(maxStack + 4, maxLocals);
        }
    }
}
